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J. Bacteriol., Oct 1995, 5653-5660, Vol 177, No. 19
MD Island and HL Mobley
Urease is an inducible virulence factor of uropathogenic Proteus mirabilis.
Although eight contiguous genes necessary for urease activity have been
cloned and sequenced, the transcriptional organization and regulation of
specific genes within the Proteus gene cluster has not been investigated in
detail. The first gene, ureR, is located 400 bp upstream and is oriented in
the direction opposite the other seven genes, ureDABCEFG. The structural
subunits of urease are encoded by ureABC. Previously, UreR was shown to
contain a putative helix-turn-helix DNA-binding motif 30 residues upstream
of a consensus sequence which is a signature for the AraC family of
positive regulators; this polypeptide is homologous to other DNA-binding
regulatory proteins. Nested deletions of ureR linked to either ureD- lacZ
or ureA-lacZ operon fusions demonstrated that an intact ureR is required
for urea-induced synthesis of LacZ from either ureA or ureD and identified
a urea-regulated promoter in the ureR-ureD intergenic region. However, lacZ
operon fusions to fragments encompassing putative promoter regions upstream
of ureA and ureF demonstrated that no urea- regulated promoters occur
upstream of these open reading frames; regions upstream of ureR, ureE, and
ureG were not tested. These data suggest that UreR acts as a positive
regulator in the presence of urea, activating transcription of urease
structural and accessory genes via sequences upstream of ureD. To address
the role of the nonstructural regulatory and accessory genes, we
constructed deletion, cassette, and linker insertion mutations throughout
the ure gene cluster and determined the effect of these mutations on
production and regulation of urease activity in Escherichia coli.(ABSTRACT
TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Proteus mirabilis urease: operon fusion and linker insertion analysis of ure gene organization, regulation, and function
Department of Medicine, University of Maryland School of Medicine, Baltimore 21201, USA.
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